How real is real-world fiction?

I've long loved to write and tell stories, but I've had a lot to learn, over the years, about how to write and tell stories. First there was that great head-teacher who made me choose between the pencil and microphone, thus teaching me to write. Then there was the brother who told me all fiction is lies, thus teaching me not to write. Then a friend suggested how wrong it was that people never go to the bathroom in children's novels. "Maybe they do in grown-up ones," she suggested. So I starte...